The invention relates to a tunnel rock drill of the type for driving a tunnel bore optionally in open or shielded mode, and also relates to a process for driving a tunnel bore, during which process the work varies from open to shielded mode, depending on the rock surrounding the tunnel bore.
When introducing tunnel bores, it is known to apply, for example, alternatingly the two following methods, depending on the nature of the soil.
a) In the so-called open mode there is free space behind the drill head. That is, the bore wall is not covered by any components of the apparatus, such as safety guards and the like. During the boring process support systems, such as steel rings, roof bolters and/or gunite linings, can be installed into this free space. In the region, in which the desired support systems are already installed, there is a bracing device, which can be braced, for example, radially, against the outer tunnel surface in order to divert the reaction forces, which are usually transferred by the drill head over a plurality of advancement cylinders, into the rock adjacent to the tunnel bore.
Since there are no burial structures or standing supports directly behind the drill head in open mode, this process is only appropriate for introducing tunnel bores in stable formations, where there is no risk that the unsupported section of the tunnel bore will collapse.
b) In the so-called shielded mode the drill head shield, which is usually provided behind the rotating part of the drill head, exhibits a so-called shield tail, whose outside diameterxe2x80x94depending on the rock""s angle of convergencexe2x80x94is chosen somewhat smaller than the actual outside diameter of the drill head or also tapering conically toward the rear. The shield tail serves to brace the tunnel wall directly adjacent to the drill head room in order to prevent said wall from collapsing.
During the drilling process in the shielded mode a tubbing support is made inside the region covering the shield tail so as to leave space at the inside shell of the shield tail by assembling usually individual prefabricated concrete components with suitable aids into a tubular support that covers the entire tunnel wall. Since the shield tail and the tubbing support always overlap a certain amount over the longitudinal stretch of the tunnel bore, a collapsing of the tunnel wall is ruled out. Thus, the shielded method is suitable especially for introducing tunnel bores into soft rock or less stable formations.
In the shielded mode the tunnel work is done with so-called tubbing cylinders, which are provided between the (non-rotated) drill head shield and the front side of the tubbing support facing the longitudinal stretch of the bore. Hence reaction forces from tunneling and rotation pass into the tubbing support, or at the start of the shielded operation, i.e. when there is still no tubbing support, said forces pass into a steel ring, which is braced radially against the rock.
Especially in the case of longer tunnel bores these holes often extend through different rock formations, with the result that both methods have to be applied alternatingly. In this case it is well-known, as a function of the respective rock formations, to transport to the breast and to set up there different devices that are appropriate for the application of the respective method. This procedure is disadvantageous since the mandatory assembly and disassembly of both devices are time-consuming and thus the production costs of boring are significantly increased.
There exists a tunnel rock drill of this class that is made by the Wirth company in Erkelenz. It is suitable not only for use in hard rock but also in soft rock formations. That is, it works, as desired, according to the open method or according to the shielded method. This device comprises a shield tail, which always covers the tunnel space directly behind the drill head shield and which comprises two shield tail segments that mate telescopically. The telescopic overlapping of the shield tail segments takes place over a length that is greater than the maximum stroke of a plurality of advancement cylinders, provided inside the shield tail so that, irrespective of the operating state, the bore wall is completely covered by the shield tail in this region.
The advancement cylinders extend between the rear wall of the drill head shield and a bracing device, which can be bracedxe2x80x94as stated abovexe2x80x94radially against the bore wall in order to absorb the drill reaction forces, to the extent that the properties of the rock formation allow this.
In order to apply the device in the shielded mode, the bracing device has tubbing cylinders that are distributed over the circumference of the bore and that face the rear with respect to the direction of boring. Said tubbing cylinders are appropriate for bracing in the aforementioned manner against an already completed tubbing support or an installed steel ring and thus to transfer the boring reaction forces into the tubbing support when the bracing device is released.
If this tunnel rock drill is used in hard rock, the tubbing cylinders are inactive, while the bracing device is braced against the tunnel wall in order to absorb the reaction forces. The drill head advances by extending the advancement cylinders; during this advancing procedure the telescopic shield tail is simultaneously advanced. If the tunnel bore, which is advanced in this manner and by appropriately installing the bracing device afterwards, comes upon soft rock formations, the bracing device is deactivated, and the drill reaction forces are diverted in the manner already described over the tubbing cylinders into the tubbing support.
Of course, this device can also be used to drive the tunnel bore in alternating rock formations without the need of the time-consuming, complete retrofitting of the tunnel rock drill. However, the drawback is that, since the telescopic shield tail is always extended during the boring operation, significant lengths of the tunnel bore area adjacent to the drill head room are covered by the shield tail. Thus, on the one hand, it is not possible to install the desired support systems in the tunnel wall directly next to the drill head room in the case of hard rock; on the other hand, the length of the shield tail prevents any changes in direction. Furthermore, owing to its telescopic design the shield tail exhibits a recess, into which material, collapsing from the tunnel mantle, can penetrate and prevent the shield from being extended and thus prevent or even block the advancement. This is especially problematic when rock formations, which have a tendency to converge, necessitate the use of a shield tail that converges conically toward the rear.
The invention is based on the problem of improving to such an extent a tunnel rock drill of this class that is appropriate for both the open and the shielded mode and thus for driving the tunnel bore in both hard rock and soft rock formations that these drawbacks are remedied.
The problem is solved by a tunnel rock drill comprising a drill head; a shield tail, which is connected to the drill head and which covers optionally at least in part the bore wall over a defined length; a bracing device, which can be optionally fixed in the tunnel bore and which serves to divert the reaction forces generated by the boring process; at least one optionally activatable advancement device, which, on the one hand, rests on the bracing device, and, on the other hand, acts on the drill head in order to drive the drill head with advancing forces in the open mode; at least one optionally activatable force generator, which has a variable length and which, on the one hand, rests on the tubbing support or an abutment for the tubbing support and, on the other hand, acts on the drill head in order to drive the drill head with advancement forces in shielded mode; and an inner kelly, which can be moved in the direction of boring in relation to the bracing device and whose breast-sided end bears the drill head, and by hinging the at least one advancement device to the inner kelly.
Since the tunnel rock drill comprises an inner kelly, which can be moved with respect to the bracing device and whose breast-sided end bears the drill head and the advancement devices are hinged to the inner kelly, the bore area directly adjacent to the drill head room is no longer covered by the advancement devices so that this design alone results in better access to the bore wall. Furthermore, this design makes it possible to arrange the permanent parts of the advancement device that rest on the bracing device in such a manner that only the moveable components of the advancement devices project in principle beyond the breast. Thus, this design eliminates the need for a telescopic design of the shield tail, as compared to the device of this class, and its length can be reduced. Hence it is much easier to change directions during the tunnel boring operation.
A design in which the shield tail is designed in such a manner that the bore wall area covered by the same can be exposed as desired is especially advantageous. This measures allows the length of the constantly covered bore area to be decreased even more, with the result that, on the one hand, the support systems to be installed in the hard rock can be placed even closer behind the breast and, on the other hand, an even tighter change in direction can be attained. The design, according to claim 2, can be made, for example, in that the shield tail comprises several pipe segments, which are divided in the longitudinal direction and can be either removed from the drill head shield or attached so as to fold over in the direction of the bore center.
The inner kelly is also preferably in the bracing device itself, and in particular can be slid longitudinally, but is rotationally rigid. Owing to these measures the inner kelly is always in essence in the bore center so that there always remains maximum space to install the support systems at the bore wall. On the other hand, instantaneous reaction forces can also be transferred over the inner kelly and the bracing device into the rock formation, forming the bore wall.
Preferably there is then a drive block, with which the drill head can be set into rotation, between the drill head and the inner kelly. In so doing, the drive block is designed in such a manner that the drive reaction moments are introduced directly into the inner kelly.
In an especially preferred embodiment of the tunnel rock drill of the invention, the drill head is hinged to the inner kelly, and in particular in such a manner that in operation the drill head""s axis of rotation can be swivelled relative to the inner kelly""s longitudinal axis. Owing to this measure, and especially in combination with a design where the inner kelly is positioned in the bracing device so as to be swivelled around an arbitrary axis perpendicular to its longitudinal axis, and owing to the possibility of minimizing the longitudinal stretch of the drill head due to the removed shield tail, an especially tight change in direction in the tunnel bore can be attained.
The drill head""s change in direction, i.e. the swivelling of its axis of rotation with respect to the bore longitudinal axis, takes place preferably with the aid of a controller, whose length can be varied and which is connected, on the one hand, to a part of the drill head or the drive block that is rotationally rigid and, on the other hand, to the inner kelly.
The drill head""s mounting on the inner kelly can be relieved, if the controller is designed in such a manner that it can serve to both transfer the advancement reaction forces from the drill head to the inner kelly and vice versa.
In a preferred design of the tunnel rock drill of the invention, the controller, the advancement devices and/or the force generators are formed by hydraulicly operated piston-cylinder units.
The articulated connections between the drill head and inner kelly and/or between inner kelly and bracing device are formed by ball joints.
The drill head is driven preferably electrically and/or hydraulicly.
A preferred embodiment of the tunnel rock drill comprises integrated means for simultaneous installation of bore supports and/or boardings during the boring operation, which are designed so as to be permanent with respect to the bore wall. With these measures the time that is required to advance a bore stroke is used to install the support systems.
The means for installing the bore supports and/or boardings are preferably arranged between the drill head and the bracing device so that the support systems can be installed directly adjacent to the drill head room.
The drill cuttings, detached from the breast, are carried away during the boring operation preferably with the aid of a drill cuttings conveyor, which runs through the inner kelly. This measure does not restrict the free space required behind the drill head for the tunnel support.
The process of the invention, during which process the work varies from open to shielded mode, depending on the nature of the rock surrounding the tunnel bore, comprises, during open mode, transferring advancement forces from a bracing device over an inner kelly, which bears the drill head on its breast-side end; and, during shielded mode, introducing the advancement forces in the drill head over at least one force generator, acting between a tubbing support or an abutment for the tubbing support and the drill head.
The drawings depict one embodiment of the invention.